Preheat your oven to 180°C (350°F) and butter a baking dish to prevent sticking.
Cook the elbow macaroni in salted boiling water until just al dente, about 8 minutes, then drain and set aside.
In a large saucepan, melt the butter over medium heat, listening for a gentle sizzle and watching it turn golden.
Add the flour to the melted butter and whisk constantly for about 1 minute, until the mixture smells slightly nutty and begins to bubble.
Gradually pour in the milk, whisking continuously to create a smooth, creamy sauce that thickens and starts to bubble, about 5 minutes.
Stir in the shredded cheddar, grated Parmesan, and pumpkin puree, mixing until the cheese melts into a velvety sauce with a warm, orange hue.
Season the sauce with salt, pepper, and cayenne pepper, tasting and adjusting the spice level to your preference.
Combine the drained pasta with the cheese sauce, folding gently to coat every piece evenly and ensure a creamy texture.
Pour the cheesy pasta mixture into your prepared baking dish, spreading it out evenly.
Sprinkle extra cheese on top for a golden, bubbly crust, then bake for 20 minutes until bubbling and golden brown.
Remove from the oven and let rest for 5 minutes; the sauce will thicken slightly and the top will crisp up nicely.
Serve warm, enjoying the creamy, cheesy texture complemented by the subtle sweetness of pumpkin and a crispy top.
